1. Field of the Invention
The present invention relates to a magnetic disk apparatus using a magnetic head having a magnetoresistive film capable of detecting signals with a high signal-to-noise ratio.
2. Description of the Related Art
In recent years, a magnetic head using a current-perpendicular-to-plane magnetoresistive film (CPP-MR film) or a tunneling magnetoresistive film (TMR film) has attracted attention as a magnetic head capable of coping with the increase in the density of the magnetic disk apparatus. The magnetoresistive film used in the magnetic head noted above is of a stacked structure of shielding layer/electrode layer/magnetization free layer/nonmagnetic layer/magnetization pinned layer/antiferromagnetic layer/electrode layer/shielding layer in which a sense current is made flow in a direction perpendicular to the film plane and along the track direction to detect the recorded magnetization. In the magnetic head, the electrode layers are arranged below and above the magnetoresistive film which makes it possible to reduce the track width and, thus, to cope with the requirement for higher density.
Conventionally, a magnetic disk apparatus using a magnetic head having a CPP-MR film or TMR film noted above in combination with a longitudinal recording medium is known. In the longitudinal recording layer used in the prior art, the easy axis of magnetization is directed at random within the plane or is slightly anisotropic.
However, it has been found that, in the case of using a magnetoresistive reproduction head of the construction where a sense current is made flow in a direction perpendicular to the film plane, i.e., along the track direction, a sense current magnetic field is generated in the track width direction so as to give rise to problems. What should be noted is that the sense current magnetic field gives rise to deterioration of recorded information on the longitudinal recording medium, particularly increase in noise and deterioration of recording resolution.